This invention relates to hand tools, and in particular the invention is concerned with a compact hand tool for projecting plumb, level, and square reference beams of visible light for precise alignment.
The use of such a tool has been limited to the ability of the operator to see the projected spot or line in daylight. In cases where the laser beam is used to produce a reference spot all the energy is concentrated in the spot. This spot is visible because its brightness is higher than the background. In cases where a reference line is needed, a cylinder lens is often used to spread the beam to generate a line. Because of the resulting lower intensity, the line is difficult to see.
The invention creates a reference line using an array of discrete spots via optical diffraction. An objective of the invention is to use an array of discrete spots to determine a more visible reference line. Another objective of the invention is to provide means to ensure that the reference lines are either plumb, level or providing a 90 degree reference through the use of self-leveling pendulums. The invention is particularly useful when it includes a self-leveling laser instrument, allowing transfer of a point to a line of spots on a wall, at the same height as the point; and allowing transfer of a floor point to a ceiling, the array of projected spots being directly above the floor point, in a common vertical plane with the floor point.
A variety of survey and carpentry tools have previously employed lasers. The first laser alignment tools were manually leveled as in U.S. Pat. Nos. 3,897,637 and 3,279,070. When a beam has been used to form a reference line, a cylinder lens has been commonly used. Other means for generating a line are described in U.S. Pat. Nos. 5,283,694 and 4,589,738. Such a laser instrument, shown generally by 2 in FIG. 1, consists of a laser beam projector 4 producing a round beam 6 which is fanned out, spread, or expanded in one axis by a positive cylinder lens 8. A bubble level 10 is mounted parallel to the horizontal axis of the cylinder lens on an adjustable platform 12. A mounting frame allows the assembly to be leveled using a tangent screw 14, the laser 4 being leveled along with the platform 12. With this apparatus a horizontal line of laser light may be projected onto a surface from a level beam of light.
In FIG. 2 the apparatus of FIG. 1 produces a horizontal line 18 on the wall 20. Note that the cylindrical lens apparatus is hidden from view by the laser beam projector 4. There are several variations of this basic system in use which employ the same principles. For example, the beams may be diverging in the horizontal or vertical direction. A second orthogonally oriented level vial may be used, etc.
In contrast to the manually level laser instrument, self-leveling instruments using a rotary beam of light have been employed to improve accuracy and reliability. These typically generate a plane of light which is detected electronically. Such instruments have been described in U.S. Pat. Nos. 4,221,483 and 4,679,937. The use of a detector is required since the limited laser power is distributed over a large area. Such systems are expensive and inconvenient since the user must purchase an electronic detector and always have the electronic detector at hand. The present invention is attractive because no detector is required and a more inexpensive laser instrument may be used.
A low cost automatic self-leveling laser instrument is described in U.S. Pat. No. 5,459,932, assigned to the same assignee as the present invention. The disclosure of that patent is incorporated herein by reference. The present invention is used in conjunction with such a compact battery operated laser projector of the type described in the above mentioned patent as well as with some manually leveled laser instruments. Such a generic laser instrument can be considered as generally shown by 2 in FIG. 1.
Lasiris Inc. of Quebec, Canada, produces a laser tool for manually positioning spots of laser light used as reference in measuring, without any self-leveling ability. The spots are generated by diffraction of a laser beam.
The present invention achieves an efficient light distribution for construction alignment or layout by providing an array of discrete spots via optical diffraction, in a compact and cost effective arrangement. The level or plumb lines of laser spots, or a line of spots on a ceiling perpendicular to a reference line, can be used for locations of drilling holes, setting nails or screws, locating windows or doors, sawing lines, erecting moldings, or ledges or other operations wherein the projected arrays of spots are far easier to generate than would be the case with a plumb bob, measuring tape, carpenter's level used to transfer lines, etc. These and other objects, advantages and features of the invention will be apparent from the following description of preferred embodiments, considered along with the accompanying drawings.